Essential to normal heart function are four heart valves, which allow blood to pass through the four chambers of the heart in one direction. The valves have either two or three cusps, flaps, or leaflets, which comprise fibrous tissue that attaches to the walls of the heart. The cusps open when the blood flow is flowing correctly and then close to form a tight seal to prevent backflow.
The four chambers are known as the right and left atria (upper chambers) and right and left ventricles (lower chambers). The four valves that control blood flow are known as the tricuspid, mitral, pulmonary, and aortic valves. In a normally functioning heart, the tricuspid valve allows one-way flow of deoxygenated blood from the right upper chamber (right atrium) to the right lower chamber (right ventricle). When the right ventricle contracts, the pulmonary valve allows one-way blood flow from the right ventricle to the pulmonary artery, which carries the deoxygenated blood to the lungs. The mitral valve, also a one-way valve, allows oxygenated blood, which has returned to the left upper chamber (left atrium), to flow to the left lower chamber (left ventricle). When the left ventricle contracts, the oxygenated blood is pumped through the aortic valve to the aorta.
Certain heart abnormalities result from heart valve defects, such as valvular insufficiency. Valve insufficiency is a common cardiac abnormality where the valve leaflets do not completely close. This allows regurgitation (i.e., backward leakage of blood at a heart valve). Such regurgitation requires the heart to work harder as it must pump both the regular volume of blood and the blood that has regurgitated. Obviously, if this insufficiency is not corrected, the added workload can eventually result in heart failure.
Another valve defect or disease, which typically occurs in the aortic valve is stenosis or calcification. This involves calcium buildup in the valve which impedes proper valve leaflet movement. Treatment typically involves removal of the leaflets and replacement with valve prosthesis during conventional open surgery. In minimal invasive surgery, the prosthesis is currently implanted without resection of the native valve. Hence it can produce an inhomogeneous and non-circular calcific layer, leading to distortion and geometry change of the prosthesis and of the aortic annulus, respectively. Paravalvular leakage (PVL) and high percentage of total heart block, coronary ostia and even prosthesis-patient mismatch are of concern with a potential negative influence on longterm survival of the patient and on the durability of the implanted prosthesis. Therefore, the endovascular resection of the degenerated native heart valve would be advantageous prior to a catheter-based implantation.
The defective heart valve is typically calcified; removal of the calcified valve requires an instrument that can deliver the appropriate cutting force, at the right place and security margin/reliability. Additionally, the tissue of a diseased heart valve cannot be readily compressed or compacted for withdrawal from the site of intervention through a catheter owing to calcification. Moreover, particular debris formed by the valve needs to be contained.
US 2006/0074484 describes a system for excising a heart valve, comprising a pair of inflatable cutting devices, but the problem of removing the bulky valve through the delivery catheter is not addressed.
There is a need in the art for a device which can perform removal efficiently and accurately, and optionally position and deploy a replacement valve in a single device.